I wanted a disposal box for my #11 X-Acto blades, and didn't really like what else I found out there. This box is the perfect size to safely discard used/dull #11 X-Acto blades. Optionally, you may incorporate 1 or 2 magnets (5mm diameter by 2 or 3 mm thick) to help hold the blades in.
Also, be sure to check out this #11 X-Acto blade storage box. This is what inspired me to create the disposal box: https://www.thingiverse.com/thing:2878971
AIO Robotics PLA
If you want to include sacrificial magnets, just pause your print at each completion of the magnet recess, which when printing at .2 mm would be 16 mm and 37 mm layer heights (you may want to print with a brim to avoid accidentally separating the model from the build plate when gluing in magnets). This object is fully sealed, so if you miss your opportunity or cannot pause then you cannot insert the mags. Put a dot of superglue (or whatever your adhesive preference is) in the magnet recess and then press in magnet. If using 2 magnets, be sure polarity on both is facing the same direction.
Print in orientation provided in STL file - OPPOSITE OF PICTURED (X & blade slot down on build plate).